Devils Lake is the largest natural freshwater lake in North Dakota, and the second-largest body of water in all of North Dakota, after the man-made impoundment, Lake Sakakawea. Devils Lake is well-known for its wild variations in lake levels, with large swings between low and high water levels. In 2006, it reached a historical high elevation of 1,449.2 ft (441.7 m), an area of 216 mi² (560 km²), and a volume of 2.7 million acre-feet (3.3 km³). Devils Lake is located in Ramsey County and Benson County, approximately 200 miles north east of Bismarck. The Spirit Lake Tribe occupies most of the southern shores.

Devils Lake is an endorheic, or closed lake with a drainage basin (Devils Lake Basin) of some 3,800 mi² (9,800 km²). The lake itself collects around 86 percent of the basin's water runoff. Above a level of 1,447 ft (441 m) the lake spills into neighboring Stump Lake. At 1,459 ft (445 m) the lake flows naturally into the Sheyenne River, although the lake has not reached this level in over 1,000 years.

Under normal conditions Devils Lake is shallow, saline, and hypereutrophic (high in nutrients). During periods of excessive precipitation, however, the lake can rise considerably and be quite deep (up to 60 feet (18 m) in places) with decreased salinity due to the effects of dilution. The eutrophic nature of the lake makes it an ideal fish habitat.

Devils Lake has long been a popular destination for fishing. It has named itself the perch capital of the world, as perch fishing in the lake is exceptional, with jumbo perch averaging 1lb commonly caught. A variety of tackle is used to catch the abundant perch, small spinners, brightly coloured jigs, and live bait (minnows and worms) are all productive. In winter, the ice fishing really picks up, with live minnows fished just off bottom taking most of the catch.

Walleye and northern pike are also abundant in Devils Lake. Anglers fishing for perch, quite commonly, find themselves landing a bonus walleye or pike, since these predatory fish will stay close to the perch schools.

There are a number of boat ramps and parks around the lake which offer great access points. Sullys Hill National Game Preserve is located on the lake's southern shore. Grahams Island State Park is located on an island in the lake. Other parks on the lake include Black Tiger State Recreation Area and Shelvers Grove State Recreation Area. Recreation in the form of open water and ice fishing has been estimated to generate in excess of $20 million dollars annually for the area.

Recently, with the rise of the water levels in Devils Lake, invading species from the Red River Valley basin have begun to threaten the lake's ecosystem. The common carp may enter the system in the near future, allowing them to populate Devils Lake. The carp's ability for fast reproductive growth and the lack of predators in the lake will likely help it to dramatically increase in population. This could have drastic consequences for existing populations of game fish such as the walleye and northern pike, which could be detrimental to the sport fishing industry.

After extensive research, in 2005, biologists did conclude that there were currently no carp in the Devils Lake Basin, but some have been found within two miles (3 km). The migration of the carp appears to be stalled by the abundant cattail plants, which restricts the travel of these fish.

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